Variable displacement piston pump



J1me 1965 Q A. F. ANDERSON 3,

VARIABLE DISPLACEMENT PISTON PUMP Original Filed Aug. 20, i959 4 Sheets-Sheet l June 1, 1965 A. F. ANDERSON 3,186,352

VARIABLE DISPLACEMENT PISTON PUMP 4 Sheets-Sheet 2 Original Filed Aug. 20, 1959 INVENTOR. 72% 0991 r 1 /l.4 IT ru /s.

J1me 1965 A. F. ANDERSON VARIABLE DISPLACEMENT PISTON PUMP 4 Sheets-Sheet 3 Original Filed Aug. 20, 1959 dimer/- 1 W IH' June 1, 1965 ANDERSON 3,186,352

VARIABLE DISPLACEMENT PISTON PUMP Original Filed Aug. 20, 1959 4 Sheets-Sheet 4 mmvron E-EE- United States Patent 3,186,352 VARIABLE DISPLACEMENT PISTON PUMP Arthur F. Anderson, Livonia, Mich., assignor to Gar Wood Industries, Inc., Wayne, Mich., a corporation of Michigan Continuation of application Ser. No. 835,002, Aug. 20,

r 1959. This application Nov. 22, 1960, Ser. No. 71,033

32 Claims. (Cl. 103-162) This application is a continuation of my prior application Serial No. 835,002, filed August 20, 1959 now abandoned.

This invention relates generally to pumps and more par- 'ticularly to an improved variable displacement piston pump.

Variable displacement piston pumps usually include a rotary cylinder barrel which abuts a stationary valve face located at one end of the barrel. The barrel is provided with a plurality of cylinder bores which are arranged in a circular formation about the barrel axis and pistons are mounted for reciprocation in the cylinder bores. As the cylinder barrel revolves, the bores alternately communicate with inlet and outlet ports in the valve face.

In these pumps, two distinctly different types of structure have been utilized for reciprocating the pistons. One type of pump includes a swash plate or slipper disk which is inclined with respect to the axis of rotation of the cylinder barrel, and the pistons are spring-urged into engagement with the slipper disk. As a result, during rotation I of the cylinder barrel, the pistons are reciprocated in their cylinder bores and their movement is coordinated with the positions of the inlet and outlet ports to provide the desired pumping of fluid. In this type of pump, the pistons abut directly against the inclined disk which applies thrust to the pistons and by varying the inclination of the slipper disk the displacement of the pistons in the cylinder bores may be varied .to vary the volume of fluid delivered by the pump. Since the disk is inclined with respect to the-pistons, the reaction force applied to the end of each piston by the disk has a first component in a direction axially of the piston and a second component perpendicular to the piston axis. As a result of the latter component, which results in a cantilever loading of the unsupported projected end of each piston, the cylinder barrel must be long enough to provide adequate side support for the pistons and the pistons must be of a large enough diameter to withstand the bending load.

The second type of pump uses a drive flange, driven by the drive shaft which also rotates the cylinder barrel, for reciprocating the pistons. The drive flange is connected by ball and socket joints to the ends of connecting rods which are connected by other ball and socket joints at their opposite ends to the pistons. A tilt box supports the drive flange and can be moved to vary the angle be tween the drive flange and the cylinder barrel to vary the volume of fluid delivered by the pump. Since the side loads applied to the pistons are small, it has been found that the length of the cylinder barrel may be reduced in this type pump. However, in prior pumps of this type, it has beencommon practice either to extend the drive shaft entirely through the pump so that it is supported at both ends, or to make the support for the drive flange stationary and tilt the cylinder barrel to vary the angle of the valve plate and cylinder barrel. In either case the resulting design is quite complex and volumetric capacities have been small.

One of the objects of this'invention isto provide a rel atively simple pump which has a high capacity to size ratio. ,This is accomplished by a new combination and arrangement of known features coupled witha design capable of high speed operation. Connecting rods are utilized for driving the pistons to thereby make possible the "Ice use of smaller pistons and a shorter cylinder barrel, a cantilever support for the pump drive shaft including an overhung bearing on the valve face is provided and the cylinder bores are inclined inwardly toward the valve face to reduce the diameter of the valve port circle and thus reduce rubbing speed between the barrel and valve plate. A'ball type universal joint connection of high torque capaoity is provided between the drive shaft and the drive flange and it is nested in the unsupported end of the drive shaft in a novel manner to minimize its space requirements and to reduce the necessary distance between the cylinder barrel and the drive flange.

Another object of this invention is to provide a pump which is constructed so that it i easily assembled without any necessity for accurately aligning the pump parts during assembly. All of the pump parts are assembled on a stationary supporting structure except the tilt box and the tilting mechanism therefor which are separately assembled on the pump housing before it is applied to the support. The design of the drive flange and the radial supporting bearing therefor, which is carried by the tilt box so that the tilt box and the drive flange can be assembled by relative axial movement, facilitates assembly of the supporting structure and the housing. In many pumps of this type, the drive flange supporting housing must be accurately positioned so that it is concentric with the cylinder barrel. The necessity for such accurate positioning is avoided in the pump of this invention by providing a cantilever drive shaft in combination with a connecting shaft having universal joints at each end, whereby the drive shaft may drive the drive flange through the connecting shaft, to thereby eflect a separation of the cylinder barrel and the drive flange so that there is no necessity for a concentric relation of these par-ts.

A further object of this invention is to provide a pump of the reciprocating piston type in which there is reduced wear on the rubbing faces of the valve plate and the cylinder barrel and in which any tendency of the cylinder barrell to tilt or wobble is reduced. This is accomplished by providing a relationship of each cylinder open-ing relative to its corresponding cylinder bore such that the opening is centered with respect to a line parallel to the barrel axis which intersects the center of the working face of the piston in the bore at a point midway bet-ween the limit positions of the working face during operation of the pump.

Still a further object of this invention is to provide a pump which has an effective lubricating mechanism for maintaining the pump parts oiled during operation, and which includes an improved assembly of the tilt box and the control or actuating cylinders therefor which provides for an accurate control of the angle of inclination of the tilt box with a minimum wear of the moving parts of the control apparatus.

Still another object of this invention is to provide a pump which is simple and compact in construction and is relatively economical to manufacture. It is .to be understood also that while the structure of this invention is particularly described herein with reference to a pump, it is apparent that it i equally applicable to a fluid motor. and, consequently, the term pump in both the specification and claims is to be inclusive of both pumps and motors.

Further objects, features and advantages of this invention will become apparent from a consideration of the following description, the appended claim-sand the accompanying drawings in which: 7

FIGURE 1 is a vertical sectional view of the pump of this invention, with some parts shown in elevation for the purpose of clarity;

FIG. 2 is a fragmentary sectional view looking substantially along the line 22 in FIG. 1;

FIG. 3 is a horizontal sectional view of the pump of this invention;- I

FIG. 4 is a transverse sectional view looking substantially along the line 4-4 in FIG. 1;

FIG. 5 is a fragmentary sectional view looking substantially along the line 55 in FIG. 3;

FIG. 6 is a View of one side of the valve plate in the 'pump of this invention as seen along the line 6-6 in FIG. 1;

FIG. 7 is a sectional view of the valve plate only looking substantially along the line 7-7 in FIG. 6; and

FIG. 8 is a sectional view looking substantially along the line 88 in FIG. 1.

With reference to the drawing, the pump of this invention, indicated generally at 10, is illustrated in FIG. 1 as including a stationary supporting structure 12 which consists of a valve block 14 and a ring-shaped valve plate 16 having a central opening 17 and mounted on one side 18 of the block 14. On its side 18, the valve block 14 is formed with a. tubular projection or sleeve 20 which projects through the plate opening 17. The sleeve 20 has an enlarged inner end 22 on which the plate 16 is supported. A projection or pin 24 on the valve block 14 projects into a cavity 26 in one side of the valve 'plate 16 for preventing rotation of the valve plate 1-6 relative to the valve block 14. The pump 18 is illustrated with the plate 16 separate from the block 14 because it facilitates manufacture of these parts and so that the plate with a pair of downwardly converging fluid passages 28 and 38. The passage 28 terminates in a pair of elongated arcuate openings 32 in the side 18 of the valve block 14 and the passage 30 similarly terminates in a pair of arcuate openings 34 in the same side of the valve block. The openings 32 and 34 are concentric with the sleeve 20, and the openings 32 are on one side of a vertical plane through the axis of the sleeve 20 and the openings 34 are on the opposite side of the plane, and communicate with corresponding arcuate openings 36 and 38, respectively, which extend through the valve plate 16 and are alignable with the openings 32 and 34. The face 37 of the valve plate 1 6 which is remote from the side 18 of the valve block 14 is formed with a recess 48' between the pair of openings 36 and a similar recess 40 between the pair of openings 38 so that in effect a single elongated arcurate opening is formed on each side of a vertical plane through the axis of the plate 16 and the openings are concentric with, respect to the axis of the plate. As

'will more clearly appear hereinafter, the openings 36 function at times as fluid inlet openings for the pump and at other times as fluid discharge openings and this is also the case with the openings 38.,

A drive shaft 42 for the pump 10 is entirely supported by a combination radial and thrust bearing 44 carried by the valve block 14 and a bearing 46 supported in the sleeve at a position adjacent the outer end 48 thereof. As shown in FIG. 1, the shaft 42 projects inwardly of the pump 10 beyond the bearing 46 and has an enlarged diameter end portion 50 which is unsupported so that in effect the shaft 42 has a cantilever mounting. An axial cavity 52 in the end portion 50 of the shaft 42 communicates with a smaller diameter axial cavity 54 which extends from the cavity 52 intocthe portion of the shaft 42 disposed within the sleeve 20. The inner end ofthe outer surface of the enlarged shaft end portion 50 is formed with a shoulder 56 which is perpendicular to housing member 90 as shown in FIG. 3.

4 stantially the middle of the shaft end portion 50. In other words, the shaft end portion 50 is disposed partially within the outer end of the barrel bore 61.

The cylinder barrel 6!) so formed with a plurality of cylinder bores which are equally spaced from each other and from the axis of the cylinder barrel 60 and are inclined radially inwardly of the cylinder barrel 60 in a direction from the face 62 toward the face 58. Nine bores 78 are shown in the illustrated form of the pump of this invention and nine cylinders are preferred for the reason that the biggest proportion of the cylinder barrel 60 can be utilized for the cylinders 70 with this number. Also, in a preferred form of the invention, the bores 70 are inclined at about three degrees relative to the axis of the cylinder barrel 60.

Each bore 70 is of a cylindrical shape and extends at its outer end to the barrel face 62 and terminates at its inner end short of the barrel face 58. Combination inlet and discharge openings 72, of arcuate shape, are formed in the barrel face 58 at positions spaced equal distances from the barrel axis and communicate with the inner ends of the bores 71 Each arcuate opening 72 is concentric with the axis of the cylinder barrel 60 and is disposed a distance from the axis of the barrel 60 such that during the rotation of the cylinder barrel 60, the opening 72 is alignable with the openings 36 and 38 in the valve plate 16.

Spline teeth or ribs 51, corresponding in number to the number of cylinder bores 70, and extending longitudinally of the shaft 42, are formed on the outer surface of the shaft end portion 50 and are fitted in longitudinally extending grooves 53 formed in the outer end of the cylinder bore 61 to provide a driving connection and support the cylinder barrel 60'. The tops of the teeth 51 are cut ofi at their right hand ends as shown in FIGURES 1 and 3 so that the support for the barrel is concentrated at a point near the end of sleeve 20. As shown in FIGURE 2, the grooves 53 are formed at positions such that each groove 53 is centered with respect to a plane extending radially of the cylinder barrel 60 disposed midway between a pair of adjacent bores 70. By locating the grooves 53 in these positions, the shaft portion 58 may be of the largest possible size for a given size cylinder barrel 60 for supporting a universal joint which is as large as possible as well more clearly appear hereinafter. A coiled spring 66, positioned in the bore 61 at a location beyond the sleeve 20, has one end in abutting engagement with the shoulder 56 on the shaft end portion 50 and the opposite end in engagement with a parallel shoulder 68 in the barrel bore 61 for urging the barrel 6%) toward the valve plate 16.

Each cylinder 70 has a piston 74 slidably mounted therein for reciprocating movement so that the working face 76 of the piston is moved toward and away from the corresponding cylinder opening 72. A piston 74 carries a socket 78 for the ball shaped end 80 of a connecting rod 82 which is also formed at its opposite end with a ball 81. Each connecting rod 82 has an axially disposed fluid passageway 84 formed therein and communicating through an opening 86 in the socket member 78 and an opening 88 in the workin-gface 76 of the piston 74 with the interior of the cylinder bore 70.

The pump 10 is provided with a cup-shape housing 90 that has an open or rim end 92 of a size to be piloted on a tubular flange 94 formed on the valve block 14. When the housing member 98 is secured to the valve block 14 in a position surrounding the flange 94 it encloses the cylinder barrel 60 and the other moving parts of the pump 18. A tilt box 96 which is likewise of a cup- 'shape having a generally concave side and a generally convex side 97 and corresponding generally to the shape of the closed end of the housing member 90, as shown in FIG, 1, is disposed within and journaled on the The tilt box 96 has diametrically opposed cavities 98 in its outer surface in which bearings 100 are mounted and the bearings 100 are mounted on removable trunnions 102 carried by the housing member 90. The trunnions 102 are secured by bolts 104 to the housing member 90 and have shaft portions 106 which project through the bearings 100 to support the tilt box 96 on the housing member 91 for tilting movement about an axis at right angles to the axis of the drive shaft 42.

The cup-shaped tilt box 96 has a central opening 108 and a rim or flange portion 110 on which an internal ring bearing 112, having rollers 113 and a retainer cage 115, is press fit. Between the bearing 112 and the opening 108, the tilt box 96 is formed with a planar surface 114 which is parallel to the axis of rotation of the tilt box 96 and is provided for a purpose to appear presently.

Adjacent one of the bearings 100, the rim or flange portion 110 is formed with an arm 116 which extends radially with respect to the axis of rotation of the tilt box 96. A pin 118 extends transversely through the arm 116 and a pair of rectangular blocks 120 are rotatably mounted on the pin 118 and disposed on opposite sides of the arm 116. The blocks 120 are of a size to fit loosely within a rectangular cavity 122 formed by the abutting ends 124 and 126 of a pair of actuating cylinders 128 and 130, respectively, each of which has an end cavity half the size of the total cavity 122. Since the mountings and controls for the pistons 128 and 136, which are mounted in removable inserts 134 attached to the housing 90 are identical, only the mounting and control of the piston 130 is described in detail hereinafter. The piston 130 is of a hollow construction and is slidably mounted in a bore 132 formed in one of the removable inserts 134 carried by the housing member 90, and is urged toward the position illustrated in FIG. 5 by a spring assembly 136 disposed within the piston 130. In this position the ends of the pistons are in abutment and the tilt box is in its neutral position.

The assembly 136 consists of an elongated bolt 133 having a head 135, a nut 137, and provided with a loose Washer 139 which abuts the nut 137. A pair of concentric coil springs 141 extend about the bolt 133 between the head 135 and the washer 139. The assembly 136 is positioned so that the washer 139 bears against an internal shoulder 143 on the piston 130 and the bolt head 135 engages the bottom of the bore in the insert 134.

The two assemblies 136 are initially accurately adjusted so that they constitute yieldable abutments which exert no force on the pistons 128 and 130 when they are in the position corresponding to the neutral or dead center position of the tilt box 96, as seen in FIGURE 5, but which will yield and permit movement of the pistons when the fluid pressures on the pistons 128 and 130 are unequal. This adjustment is achieved by accurately positioning the nuts 137 on their respective bolts 133 so that when the tilt box is in the neutral or dead center position the washers 139 and not the tilt box will receive the full force exerted by compressed springs 141, as is clearly illustrated in FIGURE 5. Thus, when one of the pistons 128, 130 operates to move or rotate the tilt box from the neutral position the opposite springs will exert a sub stantial centering force to resist such movement, but when the tilt box is in the neutral or dead center position there will be no spring force exerted thereagainst. This arrangement has been found to be very satisfactory for minimizing hunting of the tilt box.

Also mounted on the insert 134 is a control valve assembly 138 which serves as both a safety device, to return the tilt box to the neutral positionshould the discharge pressure of the pump become excessive, and as control means for controlling the angle of the tilt box and hence the displacement of the pump during normal operating conditions. Control valve assembly 138 includes an overriding valve member 140 having thereon a plurality of grooves 143 for placing an inlet port 142 into communication with a passageway 145, communicating with bore 132. Inlet port 142 is supplied with fluid under a controlled pressure from a suitable control valve (not shown), which fluid passes from inlet port 142 through grooves 143 and passageway 145 into bore 132 to'urge the piston toward piston 128, under normal operating conditions. Control valve assembly 138 is also provided with a port 144 communicating with the pump outlet and adapted to communicate with passageway 145 when the over-riding valve member is displaced to the left, as shown in FIGURE 5. The normal operating position of the over-riding valve member 140 is illustrated in FIG- URE 5, wherein a valve spring 146 is utilized to urge the valve member 140 to the right to maintain the bore 132 in operative communication with inlet port 142 for controlling the displacement of the pump. However, should an excessive pressure develop in the pump outlet, the pressure communicated to port 144 will over-ride the force of valve spring 146 to urge the valve member 140 away from port 144, so that the high pressure therein may flow through passageway to urge cylinder 130 to the neutral position. It will be observed that when the valve member 140 has been displaced to the left by ex cessive pressure in port 144, the inlet port 142 will be taken out of primary communication with passageway 145 so that piston 131) will no longer be under the exclusive control of the control valve. When the excessive pressure drops, the valve member will return to the right to place the pump under the control of the control valve.

By mounting the control pistons 128 and 130 and the centering spring assemblies 136 for the tilt box 96 directly on the housing member 90, on which the tilt box 96 is journaled, convenient assembly of the tilt box 96 and the housing member 90 is facilitated, thereby eliminating any necessity for an interfitting of parts for controlling the movement of the tilt box when the housing member 91 is mounted on the valve block 14.

The drive flange of this embodiment, generally indicated at 150 is of a cup-like shape and comprises a generally convex side 151 and a generally concave side 153, and is formed with a heavy rim portion 156 and a hollow central portion 152 disposed radially inwardly of the rim portion 156 and provided with an axial opening 154. The drive flange 150 is nested within the tilt box 96 in a position in which the rim portion 156 is rotatably supported on and surrounded by the annular bearing 112, and a thrust bearing assembly 158 is disposed between the rim portion 156 and the tilt box surface 114. The thrust bearing assembly 15$ includes a pair of spaced plates 160 and 161 and a third plate 162 disposed therebetween and having radially extending slots in which rollers 164 are mounted and retained by a ring 166 which extends about the rollers 164 and the plate 162. The plate 161 is press fit on the tilt box 96 against the surface 114 and the plates 160 and 162 are press fit on the drive flange portion 152. As will more clearly appear hereinafter, the drive flange 150 is spring-urged toward a position maintaining the plates 160 and 161 in bearing engagement with the rollers 164.

When the pump 10 is assembled the concave side 153 of the drive flange 151 faces the cylinder barrel 60 and the drive flange rim portion 156 is quite close to the barrel end face 62. A plurality of socket members 168 corresponding in number to the number of connecting rods 82 are carried by the rim portion 156 and cooperate with the balls on the connecting rods 82 to form ball and socket joint connections between the drive flange 150 and the connecting rods 82.

To provide for driving of the drive flange 150 by the drive shaft 42, a splined shaft member 170 is drivingly connected to the drive shaft 42 by a universal joint 172 of the drive ball type disposed in the cavity 52in the drive shaft end portion 50 and to the drive, flange 150 by a similar ball-type joint 174 nested within and connected to the drive flange 150. The joint 174 is of a known type, the details of which form no part of the present invention except in respect to the manner in which it is interfitted 'end thereof.

with other parts of the pump. Joint 172 is a similar joint which has been specially modified for purposes of the present pump design.

The universal joint 172 includes an inner member 176 which isan integral part of the shaft 171), located at one A plurality of radially outwardly projecting ribs or teeth 175 formed on the inner member 176 are disposed in radial alignment with corresponding radially inwardly projecting teeth or ribs 131 on the hollow shaft end portion 50 (FIG. 2) which functions as the outer member of the joint 172. The longitudinally extending teeth 175 are provided with convex-1y curved outer surfaces or crests 180 (FIG. 3) which lie in a sphere concentric with the center of the inner member and each of which is in a facing relation with a longitudinally extending surface 182 formed on the terminal end of the corresponding tooth 181. The surfaces 182 lie in a common cylinder concentric with the axis of the outer member 58.

As shown in FIG. 2, adjacent ribs or teeth 175 define therebetween grooves 177 in the inner member 176, the grooves 1'77 being substantially semicylindrical in cross section and in radial alignment with similar grooves 191 in the inner surface of the shaft end portion 50. The

grooves 177 and 191 cooperate to form cylindrical cavities each of which is of a diameter corresponding substantially to the diameter of a drive ball 178 disposed therein. In the bottom of each groove 177 there is provided a groove 179 having a radius corresponding to the radii of a pair of centering balls 171, to be disposed in'the groove 177 on the opposite sides of and in engagement with the drive 7 ball 178 for maintaining the drive 'ball 178 in a position in which a line between the center of the joint and the center of the ball 178 bisects the angle between the axes of the inner and outer members of the joint 1'72 in ail angular positions ofthe joint.

The balls 171 and 178, which constitute drive ball assemblies, are retained in their cavities by a retaining ring 183 which is held in the cavity 52 by a snap ring 64.

"The ring 1 33 has a spherical surface 185 that faces a similar surface 187 formed in the inner end of the shaft cavity 52 and the centering balls 171 ride on the surfaces 185 and 1 87. As shown in FIG. 2, the drive balls 178 center the ball member 176 in the shaft cavity 52 so that clearance is provided between the crests 180 and 182 of the teeth 175 and 181.

The universal joint 1'74 at the opposite end of the shaft 170 includes an annular inner member 186 remov-ably splined on the shaft 179 and provided with longitudinally extending radially outwardly projecting teeth or ribs 188. The ribs 188 are provided with convex-1y curved outer end surfaces 190 which engage similar concave surfaces 192 on longitudinally extending ribs or teeth 194 formed on the drive flange 150 and extending radially inwardly thereof in radial alignment with the teeth 13%. The surfaces 1% and 192' lie in spheres concentric with the center of the innerrnember. Drive ball assemblies consisting of drive balls 196 and centering balls 117 are disposed in the cavities between radially aligned adjacent pairs of teeth 138 and 194 so that during rotation of the shaft 171% driving power is transmitted to the drive flange 150 by the'drive balls 196. The spherical outer surfaces of the ends of teeth 188 loosely fit the spherical inner surfaces of teeth 194 to hold the inner member against axial displacement. A retaining ring 198 is held within drive 'fiange 15d bymeans of a snap ring 199, to maintain centering balls 197 in position. In both joints the inner members are centered radially by the drive balls.

As shown in FIGS. 1 and 2, the cylindrical cavities for the drive balls 173 are radially aligned with the grooves 53 in the cylinder barrel 60 and the exterior shaft ribs 51 so 8 terior joint housing 51} are utilized. In the case of the splined housing 50tbis is accomplished by locating the balls 17% in cavities which project int-o the ribs 51.

Thus, as best shown in FIGURE 2, maximum load capacity for a given diameter is achieved by locating the grooves 53 in the cylinder barrel 61 in radial alignment with the solid portion thereof, and by locating the grooves 191 in shaft end portion 51 in radial alignment with ribs 51. As can be seen, this arrangement makes it possible to reduce the diameters of barrel 6t and the shaft end portion 59 without creating thin sections which would greatly reduce strength. This reduction of diameters is particularly important since it results in a desirable reduction in the sliding velocity of the cylinder barrel 61B upon valve plate 16. Alternately, it facilitates the use of higher speeds, and hence displacement per unit time, for a given sliding velocity, all without a sacrifice in strength.

As shown in FIGURES l and 3,v the ends 200 and 20.2 of the shaft 178 are of a convexly curved rounded shape so as to nest Within the concavely curved ends of a pair of lubricant distributing members 2114 and 2%, respectively. The distributing member 2114 is generally cylindrical in shape and is disposed in the outer end of the drive shaft cavity 54 against one end of a coiled spring 2118 positioned in the cavity which urges the distributing member 264 toward the right as viewed in FIG. 1 to in turn urge the shaft 1-719 toward the right. The member 2114 has an axial opening 226 extending therethrough and communicating adjacent the shaft end 200 with radial passages 223.

The distributing member 206 at the opposite end 202 of the shaft 171? has a first tubular portion 210 axially aligned with the shaft 176 and formed .at one end with a peripheral groove 212. The member 2% includes a second cylindrical portion 214 of a diameter larger than the portion 21d and disposed at the grooved end of the portion 2119 so as to form a shoulder 216 at the juncture of the portions 210 and 214 which is perpendicular to the axis of the shaft 17%.

The distributing member 206 has the portion 214 disposed within the drive fiange in engagement with the shaft end 2112 and the portion 210 projects through the drive flange opening 154 which is surrounded by a radially inwardly directed flange 218 which is opposite the groove 212 and is engageable with the shoulder 216. As a result, the distributing member 206 is loosely supported on the drive flange 15% and acts through the shoulder 216 to apply thepressure of the spring 208 to the drive flange 15% so as to hold the drive flange in the tilt box 96. I

The distributing i'nember 2% is formed with an axial through opening 229 which communicates with radial passages 222 formed in the portion 214 and with one end of a passageway 22% for lubricant which extends axially through the shaft 1713 and communicates at its opposite end with the passage 226 in the distributing member 2%.

In the use of the pump 11), the drive shaft 42 is rotated to in turn drive the cylinder barrel 60 and the drive flange 15th. Fluid is supplied to one of the valve block passages 28 or 3% so that one of the passages functions as a fluid inlet passage and the other functions as a discharge passage for fluid pumped out of the pump 19. The control 'pistons 1223 and 1311 are operated to incline the tilt box 96 relative to the face 62 of the cylinder barrel d0 so that during rotation of the drive flange 15@, the pistons 74 are reciprocated in their cylinder bores 7b. During the time the working face 76 of each piston 74 is being moved toward the cylinder opening 72,-the opening 72 is opposite a discharge opening 36 or 38 in the valve plate 16 and during movement of the working face 76 in the opposite direction, the opening 72 is aligned with an inlet opening 36 or 38 in the valve plate 16.

The fluid pressure in a cylinder bore 70 during the discharge stroke of the piston 74 therein is applied to the area 2% at the inner endof the bore so as to exert a force on the cylinder barrel 60 urging it against the adjacent face 37 of the valve plate 16. Some of this fluid leaks between the cylinder barrel 60 and the valve plate face 37 to provide a film of oil on which the cylinder barrel end face 58 rotates. The pressure of this fluid film exerts a force on the cylinder barrel 6t) tending to move it in a direction away from the valve plate 16, and the fluid pressure in the cylinder bores 76 exerts a force urging the cylinder barrel 60 toward the valve plate 16.

In order to obtain efficient operation of the pump 10 without excess wear of the rubbing faces 37 and 58, it is necessary to substantially balance these forces. If the forces are unbalanced in one direction, the cylinder barrel 60 lifts off the valve plate 16 and if the forces are unbalanced in the opposite direction the fluid film is compressed and destroyed. These forces are balanced by taking into account known factors and by relieving the valve plate face 37 according to known principles. The valve plate face 37 is relieved in the annular concentric areas indicated at 232 and 236 in FIG. 6 and the radially outwardly extending areas 234 which communicate with the area 232. Only the shaded portion of the face 37 is not relieved and engages the cylinder barrel end face 58. The shaded portion includes an annular area between the relieved areas 232 and 236 which is of a radial width such that it extends on opposite sides of the openings 36 and 38 so as to form wide lands on opposite sides of the openings 36 and 38. These lands cooperate with the fluid film to form a seal around the openings 36 and 38. One advantage of a small diameter cylinder barrel 60 is that these lands are wide enough to maintain an effective seal. The shaded portion also includes radially outwardly disposed pads 231 which form outer bearing supports and stabilize the cylinder barrel 60. The opposite side 235 of the valve plate 16 is also relieved to adjust the effective area thereof relative to the effective area of the face 37 to prevent lifting of the valve plate off the valve block.

Fluid leaks into the relieved area 236 where, by virt' e of the increased volume of the space into which the fluid has traveled, it is under substantially no pressure and flows downwardly onto the sleeve 20 for travel around the end thereof onto the intermediate portions of the drive shaft 42 and onto the bearing 46. Fluid which leaks into the relieved area 232 travels outwardly through the channels 234 into a fluid discharge passageway 249 formed in the valve block 14 and communicating with an overflow tank (not shown).

Since the passageway 24% terminates at the upper end of the housing 90, the housing 90 is substantially full of fluid at all times and the centrifugal force of the rotating cylinder barrel 6% on thisfluid moves it outwardly onto the inner surface of the housing 90 from which it flows into the central opening 168 in the tilt box 96 and into the axial opening 220 in the fluid distributing member 206 which is being rotated bythe shaft 17%. The fluid also flows onto the outer surface of the tubular portion 210 of the member 266 which acts to sling this fluid radially outwardly into the space 242 between the drive flange 154) and the tilt box 96 for radially outward flow in the passage 242 onto the thrust bearing assembly 158. This fluid flows through the bearing 158 and travels radially outwardly along the inner surface of the tilt box 96 onto the bearing 112. The loose mounting of the memher 206 on the drive'flange 150 insures a flow of fluid 10 spring 208 and also flows outwardly through the radial passages 228 to lubricate the universal joint 172.

This flow of lubricating fluid is substantially the same for all positions of the tilt box 96 since it is the rotation of the cylinder barrel 64 which moves the fluid and the cylinder barrel 60 is constantly rotating during operation of the pump 14). The ball and socket joints at opposite ends of the connecting rods 82 are lubricated by fluid flowing from the cylinder bores 70 through the piston openings 86 and the connecting rod fluid passages 84.

When the tilt box 96 is tilted in one direction about its axis of rotation, one passage 23 or 30 in the valve block 14 functions as the inlet opening for the pump and the other passage functions as the outlet opening and when the tilt box 96 is tilted in the opposite direction, the function of the passages 28 and 38 is reversed. The volume of fluid being pumped is dependent on the extent of tilting of the tilt box 96, which determines the displacement of the pistons 74, and when the tilt box 96 is in its neutral position shown in FIG. 1, in which it is not tilted in either direction, the pistons 74 are not reciprocated during rotation of the cylinder barrel 60 so that no fluid is being pumped.

In the assembly of the pump It), the drive shaft 42 is supported on the valve block 14 and moved into driving engagement with the cylinder barrel 60 prior to assembly of the housing member $0 with the valve block 14. The drive flange 150, with the connecting rods 82 and the pistons 74 mounted thereon, is then assembled with the drive shaft 42 and the cylinder barrel 60. This is readily accomplished by first mounting the universal joint 172 in the drive shaft cavity 52 with the splined shaft 179 projecting outwardly therefrom. The drive iflauge 150 is then manipulated so that the spline teeth ment of the pistons 74 into .the cylinder bores 70. Since the housing member 90 is not a part of this assembly at this time, the guiding of the pistons 74 into the cylinder bores 70 is relatively easy, and so is the guiding of the shaft 170 into the ball member 186 since the pistons 74, the cylinders 70 and the splinecl shaft 179 are completely visible.

The tilt box 96 is mounted on the trunnions 102 and the inserts 134, which carry the pistons 128 and 139, are moved into diametrically opposed openings in the housing member 96 so that the blocks 120 on the tilt box actuating arm 116 are confined within the cavity 122 formed at the abutting ends of the pistons 128 and 130.

vWith the drive shaft 42, cylinder barrel 60, and drive flange thus assembled on the valve block 14 and with the tilt box 96 and the control pistons 128 and 1 30 and the centering spring assemblies 136 therefor, assembled on the housing member 90, the housing member 99 is moved into position on the pilot flange 94 on the valve block 14. During movement of the housing member 90, the only parts on the valve block 14 and housing member 9% which must be guided into operative engagement are the drive flange 15d and the tilt box 96 which must be moved into a nested relation as shown in FIG. 1. This is readily accomplished because the drive flange 150 is of large size, relative to many of the smaller parts of the pump 10, and it is only necessary that it be guided into a supported position on the bearing 112. To facilitate such guided movement, the rear side of the rirn portion 156 of the drive flange 150 has a chamfered surface 241. Once the housing member 9%) has been guided onto the flange 94, it is secured by suitable bolts (not shown) to the valve block 14 and these bolts are the only connections that .are required in the assembly of the pump 10 since the spring 268 holds the drive flange 150 in a nested position on the drive flange 96.

During operation of the pump, the amount of fluid being pumped is readily adjusted by operation of the valve assemblies 138 to control the movement of the pistons 1.28 and 130. The cavity 12-2; at the abutting ends of the pistons 123 and 13b is slightly larger in cross section than the blocks 12% on the tilt box actuating arm 116 to accommodate the slight movement of the blocks 1259 which occurs during rotation of the arm 116 about the trunnions till. This assembly of the tilt box act-uating arm 116 with the pistons 1248 and 1% provides for accurate adjustment of the tilt box 96 with a minimum Wear of the moving parts which actuatethe tilt box.

It is seen, therefore, that many of the structural features of the pump 14 cooperate to provide a pump which has a high capacity to size ratio. In one embodiment of the invention the distance between the outer sides of the housing 9tlxand the valve block 14', measured along the shaft 42, is about twelve inches, the largest part of the housing 96 is about twelve inches in diameter, and the pump is capable of delivering 188 gallons per minute at a maximum operating pressure of 2000 p.s.i. at a drive shaft speed of 2100 rpm. The diameter of the cylinder barrel oil has a direct effect on the required width of the housing 9tlmeasured in a direction diametrically of the cylinder member 60. It is also important to keep the diameter of the cylinder barrel 6% as small as possible so as to reduce the speed of the outer peripheral port-ion of the face 58 to eliminate excessive wear of the face 58. The location of the overhung bearing 4s near the point at which the barrel 6-1) is supported on the shaft 42 makes it possible to support the barrel on a cantilever drive shaft without danger that deflection of the shaft will tilt the barrel on its valve. plate. The driving connection of the shaft 4-2 to the cylinder barrel 6% adjacent the outer face 6-2 thereof makes it possible to incline the cylinder bores 7t) inwardly so that their inner ends are located on as small a radius of the cylinderbarrel as possible. 'It is the location of the inner ends of the cylinder bores 7b which determintes the diameter of the cylinder barrel Wear face 58 where peripheral speed is so important The use of the connecting rods 82 for reciprocating the pistons '74 and the nesting of the universal joints 1'72 and 174 Within the drive shaft 42 and the drive flange 150, respectively, makes possible the use of a relatively short cylinder barrel 60, measured in a direction axially thereof, and also makes possible the location of the drive flange 156 relatively close to the rear face 6-2 of the cylinder barrel 6t Relatively small diameter universal joints liz and 174 are utilized considering the loads that 7 these joints must carry. These joints are of maximum each jointas there are cylinder bores '76, arrangedin the manner described earlier.

pacity of joints of this type increases with a decrease in their working angle and therefore the use of two joints each working at half the total angle greatly increases the capacity of the pump. In addition, it makes it unnecessary to locate the housing 9% accurately with respect to the axis of the shaft 42.

In pumps of this type in which the pistons are reciprocated by articulated piston rods from a drive flange, both the cylinder barrel and the drive flange, must be driven, but the largest torque load is that required to rotate the drive flange. For that reason in the prior art it has been common practice to drive the drive flange directly from a cantilever shaft mounted on the housing at the opposite end from the valve face and to use universal joints to rotate the cylinder barrel. As a result, the valve plate end of the pump along with all its fluid connections must be articulated, with a resulting increase in complexity. In the present design the combination of features described above makes it possible to transmit the high torque for the drive flange through the universal joints with one of the joints confined radially within the circle of the cylinders. Thus, the valve plate end of the pump may be the stationary base or support and the cylinder barrel is driven from a cantilever shaft journaled entirely on the support.

During tilting of the tilt box 96, the spline shaft 179 must move axially with respect to the drive shaft 42. Joint 172 has the inner ends of its teeth lying in a common cylinder so that the inner member 176 can shift axially with respect to the outer member 5% in order to accommodate this relative movement of the shafts 42 and 1'70. It is not necessary to confine the inner member 176 against complete axial displacement with respect to member 5t? because that function is performed by the action of spring 2% on the end of spline shaft 170.

It will be understood that. the specific construction of the improved variable displacement piston pump which is herein disclosed and described is presented for purposes of explanation and illustration and is not intended to indicate limits offthe invention, the scope of which is defined by the following claims.

What is claimed is: I

1. A variable displacement piston pump comprising a drive shaft having an axial recess at one end, a tilt box journaled on an axis extending at right angles to the axis of the drive shaft, a driving flange located adjacent said shaft end and rotatably mounted on said tilt box for rota- The operation of the pump ll) is made more smooth by locating the center of each cylinder bore opening 72 on a line (shown in FIG. 1) which is parallel to the axis 7 of the cylinder barrel on and which intersects the center of the ball $53 when the piston 74- is in a position midway between the extreme positions thereof. It has been found that this relation of the pistons 74 to the openings 72 reduces any tendency of the cylinder barrel 6% to tilt with respect to the valve plate lid.

The trunnions W2 are located so that the axis about which the tilt box'96 is rota-ted is substantially midway between the joints 172 and 174 so that the total angle is substantially equally divided between the joints. joints 1'72 and 174 are constant velocity joints but are selected because of their high torque capacity rather than the fact that they provide constant velocity. The shaft 17% makes equal angles with respect to the drive shaft 42 and the drive flange 156, during tilting of the .tilt box Q6, because the axis of tilting of the tilt box is centered between the joints 17-2 and 174 so that constant velocity joints are not required. Theoretically, only one constant velocity joint need be used in the connection between the drive shaft and the drive flange. Howeverthe load ca- The tion about an axis at right angles to said journal axis, and

a driving connection between said drive shaft and said driving flange including a connecting shaft extending between saiddrive shaft and said driving flange and a universal joint connecting said drive shaft and said connecting shaft, said journal axis for said tilt box being located at a position spaced from said universal joint so that upon rotation of said tilt box and said driving flange about said tilt box journal axis said connecting shaft moves axially with respect to said drive shaft, said universal joint including a plurality of axially extending ribs formed on the interior of said shaft recess and having their crests disposed on a cylindrical surface concentric with the drive shaft axis, an inner member fixed with respect to said connecting shaft and having an equal number of axially extending external ribs having their crests convexly curved in a direction axially of said connecting shaft and disposed in substantial radial alignment with adjacent crests on said internal ribs, said shaft recess and said inner member having radially aligned mating grooves formed therein on opposite sides of said ribs, and driving balls located in the spaces between adjacent internal and external ribs.

2. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having a splined axial bore therethrough and one end face bearing against said valve face and outlet passageways; a cantilever drive shaft journaled on said supporting structure and having an unsupported splined end projecting into said axial bore in said barrel, said unsupported end drivingly engaging said barrel and constituting the sole support for said barrel against movement in a direction transverse to the rotational axis thereof; a tilt box journaled on an axis extending at right angles to the barrel axis; a driving flange journaled on said tilt box for rotation about an axis at right angles to the tilt box journal axis; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange.

3. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure and having an unsupported end projecting into said axial bore in said barrel, said unsupported end supporting and drivingly engaging said barrel and having an axial cavity in the free end thereof; a tilt box journaled on an axis extending at right angles to the barrel axis; a driving flange journaled on said tilt box for rotation about an axis at right angles to the tilt box journal axis; a piston in each cylinder bore; a connecting rod for each piston, each of said connecting rods having a ball and socket connection at one end with its piston and at the other end with said driving flange; and a driving con nection between said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in said cavity, an inner member extending into said cavity and having an equal number of axially extending external grooves in axial and radial alignment with said grooves in said cavity, and driving balls positioned in the spaces defined by aligned internal and ex ternal grooves. Y

4. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary 14 rel being formed with axially extending grooves in said axial bore thereof for receiving said spline teeth, each of said grooves having its axis disposed in a radial plane containing the axis of said barrel and positioned angularly between a pair of adjacent cylinder bores; a tilt box journaled on an axis extending at right angles to the barrel axis; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange.

6. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein equally spaced from each other and from the axis of said barrel, said barrel having an axial bore therethrough and one end face bearing against said valve face for commu'nicatingsaid cylinder bores withsaid inlet and outlet passageways; a cantilever drive shaft journaledon said supporting structure and having an unsupported end pro- .jecting into said axial bore in said barrel; a driving connection between said unsupported end and said barrel including spline teeth on said drive shaft corresponding in number to the number of said cylinder bores, said barrel being formed with axially extending grooves in said axial I here thereof for receiving said spline teeth, each of said grooves having its axis disposed in a radial plane containing the axis of said barrel and positioned angularly between a pair of adjacent cylinder bores; a driving flange; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange.

7. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel havinga plurality of cylinder bores therein, said barrel having a splined axial bore therethrough and one end .face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways, the spline teeth in said bore being equal in number to and radially aligned withsaid, cylinder bores;

..a cantilever drive shaft journaled on said supporting struccylinder barrel having a plurality of cylinder bores therein,

said barrel having a splined axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a sleeve on said stationary supporting structure extending into said axial bore in said barrel; a cantilever drive shaft journaled on said supporting structure and having a unsupported splined end extending through said sleeve into said axial bore in said barrel to drivingly engage said barrel, said drive shaft constituting the sole support for said barrel against movement in a direction transverse to the rotational axis thereof; a supporting bearing for said shaft carried by said sleeve adjacent the outer end thereof; a tilt box journaled on an axis extending at right angles to the barrel axis; a driving flange journaled .on said tilt box for rotation about an axis at right angles 'to the tilt box journal axis; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange.

5'. A variable displacement piston pump comprising: a

. stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways;

- a cantilever drive shaft journaled on said supporting structure and having? an unsupported splined end projecting 45 supporting and drivingly engaging said barrel and having into said axial bore in said barrel, said unsupported end an axial cavity in Tthefree end thereof; a tiltbox journaled on an axis extending at right angles to the barrel axis; a

. said unsupported end of said drive shaft.

8. A variable displacement piston pump comprising:

, a stationary supporting structure having a valve face and inlet and'outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure and drivingly engaging said barrel, said driveshaft having an axial cavity in the free end thereof;

a driving flange; a piston in each cylinder bore connected rto sa d driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in said cavity, an inner member extending into said cavity and having an equal number of axially extending external grooves in axial and radial alignment with said grooves in said cavity, and driving balls positioned in the spaces defined by aligned internal and external grooves.

9. A variable displacement piston pump comprising:

a stationary supporting structure having a valve :face and inlet and outlet passageways opening at said face; a rotary .cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder boresfwith said inlet and outlet passageways; a-cantilever drive shaft journaled on said supporting structure and drivingly engaging. said barrel, said drive shaft having an axial cavity in the free end thereof; a tilt box journaled on an axis extending at right angles to the barrel axis; a driving flange journaled on said tilt box for rotation about an axis at right angles to the tilt box journal axis; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in said cavity, an inner member extending into said cavity and having an equal number of axially extending external grooves in axial and radial alignment with said grooves in said cavity, and driving balls positioned in'the spaces defined by aligned internal and external grooves. J

10. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet pasdriving flange; and a driving connection between said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in said cavity, an inner member extending into said cavity and having an equal nunrber of axially extending external grooves in axial and radial alignment with said grooves in said cavity, and driving balls positioned'in the spaces defined by aligned internal-and external grooves.

11, A variable displacement piston pump comprising:-

a stationary supporting structure having. a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communica'ting said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure and having'an unsupported end projecting into said axial bore and drivingly engaging'said barrel; a driving flange having an axial cavity therein; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of axially extending 7 internal grooves formed in said cavity, an inner member extending into said cavity and having an equal number of axially extending external grooves in axial and radial alignment with said grooves in said cavity, and driving balls positioned inflthe spaces defined by aligned internal and external grooves.

porting structure and drivingly engaging said barrel, said drive shaft having an axial cavity in the free end thereof;

Ia driving flange; a piston in each cylinder bore connected to said driving flange; and a driving connection between -areassa is) said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in said cavity, an inner member extending into said cavity and having an equal number of axially extending external grooves in axial and radial alignment with said grooves in said cavity, an driving balls positioned in the spaces defined by aligned internal and external grooves, the crests of the ribs between said internal grooves in said cavity being substantially straight in the axial direction and the crests of the ribs between said external grooves on said inner member being convex in the same direction.

13. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for comrnunicatingsaid cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure, the unsupported free end of said drive shaft supporting and drivingly engaging said barrel and having an axial cavity in the end thereof; a tilt box journaled on an axis extending at right angles to the barrel axis; a driving flange journaled on said tilt box for rotation about an axis at right angles to the tilt box journal axis; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in said cavity, an inner member extending into said cavity and having an equal number of axially extending external grooves in axial and radial alignment with said grooves in said cavity, and driving balls positioned in the spacesdeflned by aligned internal and external grooves, the crests of the ribs between said internal groove-sin said cavity being substantially straight in the axial direction and the crests of the ribs between said external grooves on said inner member being convex in the same directionl 14. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft 'journ aled on said supporting structure and having an unsupported end projecting into said axial'bore in said bar-rel, said unsupported end supporting and drivingly engaging said barrel and having an axial cavity in the free end thereof; a tilt box journaled on an axis extending at right angles to the barrel axis; a driving flange journaled on said tilt box for rotation about an axis at right angles to the tilt box journal axis; a piston in each cylinder bore; a connecting rod for-teach piston, each of said connecting rods having a ball and socket connection at one end with its piston and at the other end with said driving flange; and a drivmg connection between said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in said cavity, an inner member extendmg into said cavity and having an equal number of axially extending external grooves in axial-and radial alignment with said grooves in said cavity, and driving balls positioned'in the spaces defined by aligned internal and external grooves, the crests of the ribsbetween said internal grooves in said cavity being substantially straight in the axial direction and the crests of the ribs between said external grooves on said inner member being convex in the ame direction. 15. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein equally spaced from each other and the axis of said barrel, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure and having an unsupported end projecting into said axial bore in said barrel and having an axial cavity in the free end thereof; a driving connection between said drive shaft and said barrel including spline teeth on said shaft corresponding in number to the number of said cylinder bores, said barrel being formed with axially extending grooves in said axial bore thereof for receiving said spline teeth, each of said grooves and spline teeth having the axis thereof disposed in a radial plane containing the axis of said barrel and positioned angularly between a pair of adjacent cylinder bores; a driving flange; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in said cavity, an inner member extending into said cavity and having an equal number of axially extending external grooves in axial and radial alignment with said grooves in said cavity, and driving balls positioned in the spaces defined by, aligned internal and external grooves, said internal grooves in said cavity being equal in number to said spline teeth on said shaft and being located in the same said planes as said spline teeth.

16. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein equally spaced from each other and the axis of said barrel, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure and having an unsupported end projecting into said axial bore in said barrel and having an axial cavity in the free end thereof; a driving connection between said drive shaft and said barrel including spline teeth on said shaft corresponding in number to the number of said cylinder bores, said barrel being formed with axially extending grooves in said axial bore thereof for receiving said spline teeth, each of said grooves and spline teeth having the axis thereof disposed in a radial plane containing the axis of said barrel and positioned angularly between a pair of adjacent cylinder bores; a tilt box journaled on an axis extending at right angles to the barrel axis; a driving flange journaled on said tilt box for rotation about an axis at right angles to the tilt box journal axis; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange including a'plurality of axially extending internal grooves formed in said cavity, an inner member extending into said cavity and having an equal number of axially extending external grooves in axial and radial alignment with said grooves in said cavity, and driving balls positioned in the spaces defined by aligned internal and external grooves, said internal grooves in said cavity being equal in number to said spline teeth on said shaft and being located in the same said planes as said spline teeth.

17. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rota-ry cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for cornniunicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure and drivingly engaging said barrel, said drive shaft having an axial cavity in the free end thereof; a driving flange having an axial cavity therein; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in each of said cavities, an inner member extending into each of said cavities and having at each end thereof a plurality of axially extending external grooves corresponding in number to and in axial and radial alignment with said grooves in the corresponding cavity, and driving balls positioned in the spaces defined by the aligned internal and external grooves in each of said cavities.

18. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure and drivingly engaging said barrel, said drive shaft having an axial cavity in the free end thereof; a driving flange; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in said cavity, an inner member extending into said cavity and having an equal number of axially extending external grooves in axial and radial alignment with said grooves in said cavity, driving balls positioned in the spaces defined by aligned internal and external grooves, a plurality of guide surfaces in said cavity, a smaller groove disposed in the bottom of each of said external grooves, and centering means positioned in each of said smaller grooves and coacting with said guide surfaces to position each of said driving balls.

19. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure and having an unsupported end projecting into said axial bore in said barrel and having an axial cavity in the free end thereof; a driving connection between said drive shaft and said barrel including spline teeth on said shaft, said barrel being formed with axially extending grooves in said axial bore thereof for receiving said spline teeth; a driving flange; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in said cavity, an inner member extending into said cavity and having an equal number of axially extending external grooves in axial and radial alignment with said grooves in said cavity, and driving balls positioned in the spaces defined by aligned internal and external grooves, said internal grooves in said cavity being equal in number to said spline teeth on said shaft and being located in radial and substantially axial alignment therewith.

20. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrelhaving a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said sup porting structure and having an unsupported end projecting into said axial bore in said barrel, said unsupported end supporting and drivingly engaging said barrel and having an axial cavity in the free end thereof; a driving flange; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of axially extending internal grooves formed in said cavity, an inner member extending into said cavity and having an equal number of axially extending external grooves in axial and radial alignment with said grooves in said cavity, driving balls positioned in the spaces defined by aligned internal and external grooves, a plurality of guide surfaces in said cavity, a smaller groove disposed in the bottom of each of said external grooves, and centering means positioned 'in each of said smaller grooves and coacting with said guide surfaces to position each of said driving balls.

21. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening in said face; a rotary cylinder barrel having an axis and a pair of spaced end faces, one of which is in bearing engagement with said valve face, said barrel having a splined axial bore therethrough and a plurality of substantially straight cylinder bores extending from the opposite end face to positions adjacent said one end face, said bores being spaced substantially equal distances from the axis of said barrel and from each other, each of said cylinder bores having its longitudinal axis inclined radially inwardly of the barrel in a direction toward said one end face; pistons mounted for reciprocation in said cylinder bores; a cantlever drive shaft journaled on said supporting structure and having an unsupporting splined end projecting into said axial bore in said barrel, said unsupported end drivingly engaging said barrel and constituting the sole support for said barrel against movement in a direction transverse to the rotational axis thereof; a tilt box journaled on an axis extending at right angles to the barrel axis; a driving flange journaled on said tilt box for rotation about an axis at right angles to the tilt box journal axis; a driving connection between said drive shaft and said driving flange; connecting rods providing a driving connection between said driving flange and each of said pistons, each of said connecting rods having a ball and socket connection with its piston; and means defining openings in said one end face communicating respectively with said cylinder bores, each of said openings being located so that a line parallel to said barrel axis passing through the center of the ball and socket joint between the piston in said cylinder bore and its connecting rod when the piston is midway in its stroke intersects substantially the center of said opening.

22. In a variable displacement pump of the reciprocating piston type having a supporting structure provided with a valve face and inlet and outlet passageways opening in said face, a rotary cylinder barrel having an axial bore therethrough and a pair of spaced end faces, one of which is in bearing engagement with said valve face, and a driving member for supporting and driving said barrel: means defining a plurality of spline teeth in said axial bore; means defining a plurality of axial grooves in said driving member, said grooves being drivingly engaged by said spline teeth; means defining a plurality of cylinder bores in said barrel extending from the opposite end face to positions adjacent said one end face, said cylinder bores being spaced substantially equal distances from the rotational axis of said barrel and from each other, said teeth and said cylinder bores being equal in number and radially aligned; means defining a plurality of openings in said one end face communicating respectively with said cylinder bores; a driving flange; and pistons mounted for reciprocation in said cylinder bores and engaging said driving flange to be reciprocated thereby.

23. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; means defining an axial counterbore in said barrel having a splined portion therein; a cantliver drive shaft journaled on said supporting structure and having tilt box for rotation about an axis at right angles to the tilt box journal axis; a piston at each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange.

2-4. A pump as claimed in claim 23, wherein said splined portion on said drive shaft engages said splined portion in said barrel only adjacent the end of said barrel farthest from said valve face.

i 25. A variable displacement piston pump, comprising:

a stationary supporting structure having a valve face; inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating saidcylinder bores with said inlet and said outlet passageways; a cantilever drive shaft journaled on said supporting structure and projecting into said axial bore in said barrel; means defining an axial cavity in'the free end of said drive shaft; a driving connection between said drive shaft and said barrel including spline teeth on said shaft and grooves in said axial bore of said barrel for receiving said spline teeth; a driving flange; a piston in each cylinder bore connected to said driving flange; and a driv ing connection between said drive shaft and said driving flange including a plurality of internal grooves formed in said cavity, and an inner member extending into said cavity and having drive means engaging said grooves in said cavity, said grooves in said cavity being equal in number to said spline teeth on said drive shaft and being located in radial and substantially axial alignment therewith.

26. A variable displacement piston pump, comprising: a stationary supporting structure having a valve face; inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and said outlet passageways; a cantilever drive shaft journaled on said supporting structure and projecting into said axial bore in said barrel; means defining an axial cavity in the free end of said drive shaft; a driving connection between said drive shaft and said barrel including spline teeth on said shaft and grooves in said axial bore of said barrel for receiving said spline teeth; a driving flange; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of internal grooves formed in said cavity, and an inner member extending into said cavity and having drive means engaging said grooves in said cavity, said grooves in said cavity being equal in number to said spline teeth on said drive shaft and being located in radial and substantial axial alignment therewith, and said spline teeth on said drive shaft being equal in number to said cylinder bores and lying in radial planes containing the axis of said drive shaft and extending between adjacent cylinder bores.

27. A variable displacement piston pump, comprising: a stationary supporting structure having a valve face; inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and said outlet passageways; a cantilever drive shaft journaled on said supporting structure and projecting into said axial bore in said barrel; means defining an axial cavity in the free end of said drive shaft; a driving connection between said drive shaft and said barrel including spline teeth on said shaft and grooves in said axial bore of said barrel for receiving said spline teeth; a driving flange; a piston in each cylinder bore connected to 'said driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of internal grooves formed in said cavity, and an inner member extending into said cavity and having drive means engaging said grooves in said cavity, said spline teeth on said drive shaft being equal in number to said cylinder bores and lying in radial planes containing the axis of said drive shaft and extending between adjacent cylinder bores.

28. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having an axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure and projecting into said axial bore in said barrel; means defining an axial cavity in the free end of said drive shaft; a driving connection between said drive shaft and said barrel including spline teeth on said shaft and grooves in said axial bore in said barrel for receiving said spline teeth; a driving flange; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange including a plurality of internal grooves formed in said cavity, an inner member extending in said cavity and having an equal number of external grooves in axial and radial alignment with said grooves in said cavity, and driving balls positioned in the spaces defined by said aligned internal and external grooves, said spline teeth on said drive shaft being equal in number to said cylinder bores and lying in radial planes containing the axis of said drive shaft and extending between adjacent cylinder bores.

29. A variable displacement pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein equally spaced from each other and from the axis of said barrel, said barrel having an axial bore therethrough and one end face bearing against said valve face for connecting said cylinder bores with said inlet and outlet passageways; a drive shaft journalled on said supporting structure and projecting into said axial bore in said barrel; a driving connection between said drive shaft and said barrel including spline teeth on said drive shaft corresponding in number to the number of said cylinder bores, said barrel being formed with axially extending corresponding grooves in said axial bore thereof for receiving said spline teeth, each of said grooves having its axis disposed in a radial plane containing the axis of said barrel and positioned angularly between a pair of adjacent cylinder bores, the spline teeth on said drive shaft being substantially shorter in effective axial length than the length of said bore in said cylinder barrel and adapted to engage said grooves in said axial bore only adjacent the end of said barrel farthest from said barrel face; a driving flange; a piston in each cylinder bore connected to said driving flange; and a driving connection between said drive shaft and said driving flange.

30. A variable displacement pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein equally spaced from each other and from the axis of said barrel, said barrel having an axial bore therethrough and one end face bearing against said valve face, each of said cylinder bores having its longitudinal axis inclined radially inwardly of said barrel in a direction toward said one end face; a drive shaft journaled on said supporting structure and projecting into said axial bore in said barrel; a driving connection between said drive shaft and said barrel including spline teeth on said drive shaft corresponding in number to the number of said cylinder bores, said barrel being formed with axially extending corresponding grooves in said axial bore thereof for receiving said spline teeth, each of said grooves having its axis disposed in a radial plane containing the axis of said barrel and positioned angularly between a pair of adjacent cylinder bores, the spline teeth on said drive shaft being substantially shorter in effective axial length than the length of said bore in said cylinder barrel and adapted to engage said grooves in said axial bore only adjacent the end of said barrel farthest from said barrel face; a driving flange; a piston in each cylinder bore; con necting rods providing a driving connection between said driving flange and each of said pistons, each of said connecting rods having a ball and socket connection with its piston; means defining openings in said one end face of said barrel communicating respectively with said cylinder bores, each of said openings being located so that a line parallel to said barrel axis passing through the center of the ball and socket joint between the piston in said cylinder bore and its connecting rod when the piston is midway in its stroke intersects substantially the center of said opening; and a driving connection between said drive shaft and said driving flange.

31. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having a splined axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure and having an unsupported splined end projecting into said axial bore in said barrel, said unsupported end drivingly engaging said barrel and constituting the sole support for said barrel against movement in a direction transverse to the rotational axis thereof; a tilt box journalled on an axis extending at right angles to the barrel axis; a driving flange journaled on said tilt box for rotation about an axis at right angles to the tilt box journal axis; a piston in each cylinder bore; a connecting rod for each piston, each of said connecting rods having a ball and socket connection at one end with its piston and at the other end with said driving flange; and a driving connection including a universal joint extending between said drive shaft and said driving flange.

32. A variable displacement piston pump comprising: a stationary supporting structure having a valve face and inlet and outlet passageways opening at said face; a rotary cylinder barrel having a plurality of cylinder bores therein, said barrel having a splined axial bore therethrough and one end face bearing against said valve face for communicating said cylinder bores with said inlet and outlet passageways; a cantilever drive shaft journaled on said supporting structure and having an unsupported splined end projecting into said axial bore in said barrel, said unsupported end drivingly engaging said barrel and constituting the sole support for said barrel against movement in a direction transverse to the rotational axis thereof; means defining an axial cavity in the unsupported end of said drive shaft; a tilt box journaled on an axis extending at right angles to the barrel axis; a driving flange journaled on said tilt box for rotation about an axis at right angles to the tilt box journal axis; a piston in each cylinder bore; a connecting rod for each piston, each of said connecting rods having a ball and socket connection at one end with its piston and at the other end with said driving flange; and a driving connection including a universal joint extending between said drive shaft and said driving flange, at least a portion of said universal joint being positioned within said axial cavity.

References Cited by the Examiner UNITED STATES PATENTS Egersdorfer 103-162 Rose a- 103-162 Gros 103-162 Herrstrum 74-60 Tweedale 103-162 Dodge 64-8 Robinson 103-162 Minshall et a1. 103-162 Klopp 103-162 Buchner 103-162 24 2,908, 151 10/ 5 9 Nahhnark 64-12 1 2,956,508 10/60 Wahlmark 103-162 3,017,756 1/62 Sharp 64-21 V FOREIGN PATENTS 525,162 7/53 Canada.

522,717 3/ 27 Germany. 941,343 4/56 Germany. 1,034,980 7/58 Germany. 10 1,037,799 8/58 Germany. 1,046,434 12/5 8 Germany,

ROBERT M. WALKER, Primary Examiner. 7

LAURENCE V. EFNER, Examiner. 

1. A VARIABLE DISPLACEMENT PISTON PUMP COMPRISING A DRIVE SHAFT HAVING AN AXIAL RECESS AT ONE END, A TILT BOX JOURNALED ON AN AXIS EXTENDING AT RIGHT ANGLES TO THE AXIS OF THE DRIVE SHAFT, A DRIVING FLANGE LOCATED ADJACENT SAID SHAFT END AND ROTATABLY MOUNTED ON SAID TILT BOX FOR ROTATION ABOUT AN AXIS AT RIGHT ANGLES TO SAID JOURNAL AXIS, AND A DRIVING CONNECTION BETWEEN SAID DRIVE SHAFT AND SAID DRIVING FLANGE INCLUDING A CONNECTING SHAFT EXTENDING BETWEEN SAID DRIVE SHAFT AND SAID DRIVING FLANGE AND A UNIVERSAL JOINT CONNECTING SAID DRIVE SHAFT AND SAID CONNECTING SHAFT, SAID JOURNAL AXIS FOR SAID TILT BOX BEING LOCATED AT A POSITION SPACED FROM SAID UNIVERSAL JOINT SO THAT UPON ROTATION OF SAID TILT BOX AND SAID DRIVING FLANGE ABOUT SAID TILT BOX JOURNAL AXIS SAID CONNECTING SHAFT MOVES AXIALLY WITH RESPECT TO SAID DRIVE SHAFT, SAID UNIVERSAL JOINT INCLUDING A PLURALITY OF AXIALLY EXTENDING RIBS FORMED ON THE INTERIOR OF SAID SHAFT RECESS AND HAVING THEIR CRESTS DISPOSED ON A CYLINDRICAL SURFACE CONCENTRICL WITH THE DRIVE SHAFT AXIS, AN INNER MEMBER FIXED WITH RESPECT TO SAID CONNECTING SHAFT AND HAVING AN EQUAL NUMBER OF AXIALLY EXTENDING EXTERNAL RIBS HAVING THEIR CRESTS CONVEXLY CURVED IN A DIRECTION AXIALLY OF SAID CONNECTING SHAFT AND DISPOSED IN SUBSTANTIALLY RADIAL ALIGNMENT WITH ADJACENT CREATS ON SAID INTERNAL RIBS, SAID SHAFT RECESS AND SAID INNER MEMBER HAVING RADIALLY ALIGNED MATING GROOVES FORMED THEREIN ON OPPOSITE SIDES OF SAID RIBS, AND DRIVING BALLS LOCATED IN THE SPACES BETWEEN ADJACENT INTERNAL AND EXTERNAL RIBS. 